MediaPlayer™ versus RealPlayer™ - A Comparison of Network Turbulence

The development of higher speed Internet connections and improvements in streaming media technology promise to increase the volume of streamed media over the Internet. The performance of currently available streaming media products will play an important role in the network impact of streaming media. However, there are few empirical studies that analyze the network traffic characteristics and Internet impact of current streaming media products. This paper presents analysis from an empirical study of the two dominant streaming multimedia products, RealNetworks RealPlayer™ and Microsoft MediaPlayer™. Utilizing two custom media player measurement tools, RealTracker and MediaTracker, we are able to gather application layer and network layer information about RealPlayer and MediaPlayer for the same media under the same network conditions. Our analysis shows that RealPlayer and MediaPlayer have distinctly different behavior characteristics. The packet sizes and rates generated by MediaPlayer are essentially CBR while the packet sizes and rates generated by RealPlayer are more varied. During initial delay buffering, MediaPlayer sends data at the same rate as during playout while RealPlayer can buffer at up to three times the playout rate. For high bandwidth clips, MediaPlayer sends frames that are larger than the network MTU, resulting in multiple IP fragments for each application level frame. From the application perspective, for low bandwidth clips, MediaPlayer has a lower frame rate than RealPlayer. Our work exposes some of the impact of streaming media on the network and provides valuable information for building more realistic streaming media simulations

Teaching Technology Fellowship Report on “Demonstration/Measurement System for Wireless Networks”

This paper is the final report for a Teaching Technology Fellowship project conducted between July 2005 and May 2007. This project involved integrating a wireless network measurement experiment into the curriculum of CS4514, Computer Networks, during the WPI B06 undergraduate term. After presenting goals and objectives, the chronology of preparation and execution of the project plan are discussed. The paper assesses the results of the B06 wireless measurement experience against a B05 offering of Computer Networks that included a wireless design assignment. A discussion of observations about the positive and negative aspects of this experimental pedagogical effort is provided as a summary

Research Resources for Network Application Studies

The growth of computer networks has led to increasing diversity of Internet applications, including streaming media and network games. However, without precise information on how network and system improvements benefit the networked application user, it is difficult to properly assess the benefits of new network treatments or to design the next generation networks that will effectively support the QoS of emerging applications. This research attempts to bridge this gap in understanding with three innovative projects: 1) integrating measures of network performance with user perception; 2) quality of service for network games; and 3) perceived quality of adaptive streaming media repair. With the requested research resources, we have developed an application performance studies laboratory that allows us to finely control network performance for a range of selected networked applications. Each project shares research resources in the new laboratory to measure performance for interactive applications, network games and streaming media repair, as appropriate

On combining temporal scaling and quality scaling for streaming MPEG

Temporal Scaling and Quality Scaling are both widely-used techniques to reduce the bitrate of streaming video. How-ever, combinations and comparisons of Temporal and Qual-ity Scaling have not been systematically studied. This re-search extends previous work to provide a model for combin-ing Temporal and Quality Scaling, and uses an optimization algorithm to provide a systematic analysis of their combina-tion over a range of network conditions and video content. Analytic experiments show: 1) Quality Scaling typically per-forms better than Temporal Scaling, with performance dif-ferences correlated with the motion characteristics of the video. In fact, when the network capacity is moderate and the loss rate is low, Quality Scaling performs nearly as well as the optimal combination of Quality and Temporal Scal-ing; 2) when the network capacity is low and the packet loss rate is high, Quality Scaling alone is ineffective, but a combination of Quality and Temporal Scaling can provide reasonable video quality; 3) adjusting the amount of For-ward Error Correction (FEC) provides significantly better performance than video streaming without FEC or video streaming with a fixed amount of FEC. 1

Leniency and halo effects in marking undergraduate short research projects

BACKGROUND: Supervisors are often involved in the assessment of projects they have supervised themselves. Previous research suggests that detailed marking sheets may alleviate leniency and halo effects. We set out to determine if, despite using such a marking schedule, leniency and halo effects were evident in the supervisors' marking of undergraduate short research projects (special study modules (SSM)). METHODS: Review of grades awarded by supervisors, second markers and control markers to the written reports of 4(th )year medical students who had participated in an SSM during two full academic years (n = 399). Paired t-tests were used to compare mean marks, Pearson correlation to look at agreement between marks and multiple linear regression to test the prediction of one mark from several others adjusted for one another. RESULTS: There was a highly significant difference of approximately half a grade between supervisors and second markers with supervisors marking higher. (t = 3.12, p < 0.01, difference in grade score = 0.42, 95% CI for mean difference 0.18–0.80). There was a high correlation between the two marks awarded for performance of the project and the written report by the supervisor (r = 0.75), but a low-modest correlation between supervisor and second marker (r = 0.28). Linear regression analysis of the influence of the supervisors' mark for performance on their mark for the report gave a non-significant result. This suggests a leniency effect but no halo effect. CONCLUSIONS: This study shows that with the use of structured marking sheet for assessment of undergraduate medical students, supervisors marks are not associated with a halo effect, but leniency does occur. As supervisor assessment is becoming more common in both under graduate and postgraduate teaching new ways to improve objectivity in marking and to address the leniency of supervisors should be sought